Automated data storage libraries are known for providing cost effective storage and retrieval of large quantities of data. The data in automated data storage libraries is stored on data storage media that are, in turn, stored on storage shelves or the like inside the library in a fashion that renders the media, and its resident data, accessible for physical retrieval. Such media is commonly termed “removable media.” Data storage media may comprise any type of media on which data may be stored and which may serve as removable media, including but not limited to magnetic media (such as magnetic tape or disks), optical media (such as optical tape or disks), electronic media (such as PROM, EEPROM, flash PROM, CompactFlash™, Smartmedia™, Memory Stick™, etc.), or other suitable media. Typically, the data stored in automated data storage libraries is resident on data storage media that is contained within a cartridge and referred to as a data storage media cartridge. An example of a data storage media cartridge that is widely employed in automated data storage libraries for mass data storage is a magnetic tape cartridge.
In addition to data storage media, automated data storage libraries typically contain data storage drives that store data to, and/or retrieve data from, the data storage media. The transport of data storage media between data storage shelves and data storage drives is typically accomplished by one or more robot accessors (hereinafter termed “accessors”). Such accessors have grippers for physically retrieving the selected data storage media from the storage shelves within the automated data storage library and transport such media to the data storage drives by moving in the X and Y directions.
In an effort to increase storage capacity, deep slot technology (or deep cartridge slots) allows for storage slots that contain more than a single cartridge. Such storage libraries allow for higher density, or more cartridges stored per square foot. In ‘deep slot’ libraries, two or more cartridges are arrayed in series so that accessing desired cartridges may require removing cartridges stored in front of the desired cartridge. As used herein, the term “deep slot” refers to a magazine or storage slot including an array of storage slots such that at least two slots are arranged in series such that accessing an interior slot requires traversing at least one exterior slot.
Deep slot technology requires that there be enough free storage space to hold the number of cartridges that can be contained in a deep slot, minus one. This is because the library may have to access the last cartridge in a deep slot, and the cartridges in front of the last cartridge must be moved out of the way. For example, if a library has storage slots that can contain 5 cartridges, then the library will need to be able to place 4 of the 5 cartridges somewhere else, while it accesses the 5th cartridge with a library gripper. This additional required space shall be referred to as “swap space”. Swap space may comprise additional storage slots, I/O slots, drive slots, gripper slots, or any other location that may be used to hold a cartridge while another cartridge is being accessed.
One problem with deep slot technology is inventory. This is because, except for the first cartridge, a bar code reader cannot see the cartridge labels in a deep slot without removal. As a result, the library must remove each cartridge to read the label of the cartridge behind it, and to ensure that there are no more cartridges to read. This can be very time consuming, and an operator may be long gone after replacing a magazine, closing a library door, or powering up a library.
What is needed is a quick method of determining that the minimum required number of storage slots are available as swap space in a deep slot library after a magazine has been placed in the library, after a library door has been closed, or after a library reset or power-on.
Furthermore, capacity on demand systems provide vendors the ability to offer their customers more physical storage capacity than the customer has paid for, while allowing an upgrade to storage capacity without installing new hardware. Such systems allow a customer greater flexibility in managing storage requirements. However, with deep slot technology, such systems run the danger to the vendor that a customer could place more cartridges in a capacity on demand system than the customer has paid for, and it would be difficult for the library to detect.
What is needed is a method of determining if more cartridges have been placed in a deep slot library than have been activated with a capacity on demand solution.
It is therefore a challenge to develop strategies for storing cartridges to overcome these, and other, disadvantages.